Radioactive material container

ABSTRACT

A shielded rack loader makes use of a loading rack movable between a shielding structure and a storage tube. A shield plug seals the storage tube. A hoist moves the shield plug and the loading rack. A shield plug cart and a material transfer cart mate with receiving flanges of the rack loader and permit temporary storage and movement of the shield plug and of canisters of transuranic material.

This application claims priority to Great Britain Application No.9910998.5 filed on May 13, 1999 and International Application No.PCT/GB00/01831 filed on May 12, 2000 and published in English asInternational Publication Number WO 00/70624 on Nov. 23, 2000.

This invention relates to a radioactive material container.

In order to prevent radiation escaping from a receptacle containing aradioactive material, it is usual to wrap lead sheeting around thereceptacle. This is then followed by binding the lead wrapped receptaclewith adhesive plastic tape. This has the inherent disadvantages ofmaking the receptacle heavy, bulky and difficult to handle and issusceptible to leaving gaps in the shielding through which radiation canescape. If the radioactive material is a liquid, then the conventionallead casing will not prevent the liquid from escaping from thereceptacle/casing ensemble in the event that the receptacle should failor break.

In accordance with the present invention a radioactive materialcontainer comprises a receptacle characterised in that a coating of leadand a further resilient layer cover a substantial proportion of thereceptacle's exterior surface the lead being deposited by anelectroplating process.

The lead may be directly coated on the surface of the receptacle.Coating of a sufficient surface area of the receptacle provides for themitigation of escape of radiation from the container. The electroplatingprocess provides for simple deposition of the required thickness oflead, which is adequately uniform across the surface area of thereceptacle. This reduces the weight of the container, which is alsoconsequently easier to handle. The lead may absorb some of the energy ofany impulse that is experienced by the container (for example, if thecontainer is dropped), thus decreasing the likelihood of breakage of thereceptacle. However its primary function is to prevent or reduce to safelevels transmission of radiation outside of the container.

The lead has a mean thickness in the range 0.01-6 mm, with a preferredmean thickness of 1 to 6 mm. Most preferably the lead thickness isbetween 1 mm to 2 mm. This provides a sensible degree of protectionwhilst being reasonably easy to apply and adhere to the receptacle.Furthermore, this is sufficient to provide protection for the user ofthe container, while retaining lightness and ease of use.

In one embodiment, the receptacle is made of a plastics material.Plastics receptacles are lightweight, readily available and cheap. Theplastics material is preferably chosen from one of high densitypoly(ethylene), poly(propylene), poly(methylpentene) andpoly(tetrafluoroethylene).

In another embodiment, the receptacle is made of glass. This material isvery strong and does not usually degrade when subjected to radiation.

In a further embodiment, the receptacle is made of a metal. Metals aregenerally strong, yet tough The metal is preferably aluminium, sincethis is lightweight.

The resilient layer is especially useful if the receptacle may bedamaged by impact or other shock which might result in mechanicalbreakage of the receptacle and allow leakage of any materials containedtherein. Such a layer is particularly advisable where the receptacle ismade from glass or a similar fragile material which is easily shatteredon impact. By applying a resilient layer the breakage can be preventedor any leakage postponed or reduced by the resilient layer. Theresilient layer is preferably applied over the lead. The material of theresilient layer is preferably an epoxy resin. This forms a hard durableand slightly flexible protective barrier which contains the receptaclecontents should the receptacle and the lead layer fail. A furtheradvantage of using epoxy resin is its tendency to expand on contact withsome radioactive materials thus acting as a warning if the integrity ofthe receptacle has been breached. This provides a period within whichthe material is still contained and enables remedial action to be takenfor example, transfer to another container. Materials other than epoxyresin suitable for use in the invention will be apparent to thoseskilled in the art.

In one embodiment, in addition to the lead coating there is at least onefurther coating of cadmium and one further coating of copper both ofwhich cover a substantial proportion of the exterior surface of thereceptacle or the lead. Preferably the receptacle is first coated withat least one layer of cadmium and a layer of copper before the lead isapplied. The cadmium and copper layers mitigate the egress of anyX-rays. Preferably at least one additional layer of cadmium and anadditional layer of copper is provided on top of the lead layer. Thisforms a sandwich with the lead in the middle. A resilient layer is thenprovided on top.

In one arrangement of the invention, a substantial proportion or thewhole of the exterior surface of the receptacle or lead coating iscoated with cadmium and copper layers.

In one embodiment, the cadmium and copper are deposited by anelectroplating process, thus enabling all of the coating to befacilitated by electroplating. The electroplated cadmium and copperlayers, may have a total range of thickness of between 0.01 and 1 mm.

The receptacle is chosen from one of a syringe, a bottle, a box or acanister.

An example of a radioactive material container in accordance with thepresent invention will now be described with reference to theaccompanying drawings of which:

FIG. 1 is a schematic cross-sectional view of a conventional radioactivematerial container in which a radioactive material has been placed;

FIG. 2 is a schematic cross-sectional view of a radioactive materialcontainer in accordance with the present invention in which aradioactive material has been placed; and,

FIG. 3 is a schematic cross-sectional view of a radioactive materialcontainer in accordance with the present invention, with a coating ofcadmium and copper on the exterior surface of the lead coating, in whicha radioactive material has been placed.

FIG. 1 shows an example of a conventional radioactive material containercomprising a plastic bottle 1, a bottle cap 2 and a antimonial leadshield 3. The bottle is partially filled with a radioactive liquid 4,for example, a crown ether complexed with a radioactive metal e.g.uranium. The lead shield 3 is made from antimonial lead sheeting whichis crudely moulded around the bottle 1 and cap 2. The antimonial leadshield 3 absorbs a significant proportion of the ionising radiation thatis emitted from the radioactive liquid 4. Hence, the amount of radiationthat is transferred to the external environment is much reduced. Certaincomponents of the radiation emitted by the radioactive liquid 4 (forexample, alpha particles) will, however, cause the plastic bottle 1 todegrade. For example, exposure to β radiation can make some plasticsvery brittle. The bottle 1 may eventually degrade to the extent that itwill totally fail or break, with the consequence that the liquid 4 willleak through to the antimonial lead shield 3. Since the shield 3 is madefrom sheets, there may be gaps in the shield through which theradioactive liquid 4 can leak. The gaps may also allow the unwantedegress of radiation.

The radioactive material container of the present invention addressesthese problems by encasing the receptacle in a continuous, yetrelatively thin layer of lead, the layer of lead being coated onto thesurface of the receptacle.

A container in accordance with the present invention is shown in FIG. 2,which comprises a plastic receptacle, in this case a conventionalsolvent bottle 5 and cap 6 (both of which are made from high densitypolyethylene) and a layer of lead 7 deposited by an electroplatingprocess on to the exterior surface of the bottle 5 and cap 6. The bottle5 could be made from any plastics material suitable for the containmentof radioactive material, the choice being affected, inter alia, by thechemical nature of the material contained therein. The layer of lead 7is typically 2-5 mm thick and is continuous over each of the bottle 5and the cap 6 i.e. it totally encases the main body of the bottle 5 andthe external surface of the cap 6. The layer of lead 7 may extend beyondthe edge of the cap 6 so that there is no interface region between thebottle 5 and cap 6 through which a significant amount of radiation canbe emitted from the container. The bottle 5 is shown partially filledwith a radioactive liquid 8, such as a crown ether which has beencomplexed with a radioactive metal e.g. uranium.

The continuous layer of lead 7 will minimise radiation egress from thebottle 5. There are no breaks or gaps in the lead through whichsignificant amounts of radiation should leak.

The layer of lead 7 is deposited by electroplating onto the exteriorsurface of the bottle 5. A container according to the present inventionwill be less bulky than that shown in FIG. 1 since the layer of lead 7is directly deposited onto the exterior surface of the bottle 5 andhence follows the contours and shape of the bottle 5, whereas, in aconventional container (FIG. 1), the lead shield 3 is manually formedaround or moulded crudely onto the bottle 1.

The probability of the bottle 5 breaking in the container according tothe invention will be slightly decreased when compared with a bottleused as a conventional container. A further layer 9 of an epoxy resin isapplied as a coating on top of the entire layer of lead 7 to ensure thatno liquid 8 will escape from bottle 5 even if this were to break orfail. This is important if the bottle 5 becomes brittle due toirradiation or if the bottle 5 is made from a fragile material such asglass.

Another example of a container in accordance with the present inventionis shown in FIG. 3, which comprises an aluminium receptacle, in thiscase a canister 10 and lid 11. A layer of lead 12 is deposited by anelectroplating process on to the exterior surface of the canister 10 andlid 11. A layer of cadmium 13 is deposited by an electroplating processon to the exterior surface of the layer of lead 12. The layer of lead 12is typically 2-5 mm thick, but may be in the range 0.01-6 mm, and iscontinuous over each of the canister 10 and the lid 11 i.e. it totallyencases the main body of the canister 10 and the external surface of thelid 11. A layer of copper 14 is deposited by an electroplating processupon the layer of cadmium 13. This reduces or eliminates emissions ofBeta radiation through the canister 10 and lid 11. The layer of lead 12may extend beyond the edge of the lid 11 so that there is no interfaceregion between the canister 10 and lid 11 through which a significantamount of radiation can be emitted from the container. The canister 10is shown partially filled with a radioactive liquid 16.

The layer of cadmium 13 is in the range of 0.01-1 mm thick and iscontinuous over the layer of lead 12 that coats each of the canister 10and the lid 11 i.e. it totally encases the main body of the canister 10and the external surface of the lid 11. As with the layer of lead 12,the layer of cadmium 13 may extend beyond the edge of the lid 11 so thatthere is no interface region between the canister 10 and lid 11 throughwhich a significant amount of radiation can be emitted from thecontainer. The continuous layer of cadmium 13 reduces the egress of fastneutrons through the canister 10 and lid 11. The layer of copper 14 isin the range of 0.01-1 mm thick and is continuous over the layer ofcadmium 13 that coats each of the canister 10 and the lid 11 i.e. ittotally encases the main body of the canister 10 and the externalsurface of the lid 11. As with the layer of cadmium 13 the layer ofcopper 14 may extend beyond the edge of the lid 11 so that there is nointerface region between the canister 10 and lid 11 through which asignificant amount of radiation can be emitted from the container. Thecontinuous layer of copper 14 reduces the egress of fast neutronsthrough the canister 10 and lid 11. The canister 10 and lid 11 arecovered by an epoxy resin layer 15 which acts to prevent failure of thecanister 10 or lid 11 or restrict the outflow of any contents in theevent of any failure because of impact.

What is claimed is:
 1. A radioactive material container comprising areceptacle having an exterior surface and comprising: a. a lead coatingelectroplated onto at least a portion of the exterior surface, the leadcoating having a mean thickness in the range 0.01-6 mm; and b. a furtherresilient layer covering at least a portion of the exterior surface orthe lead coating.
 2. A radioactive material container according to claim1 in which the mean thickness of the lead coating is approximately 1-2mm.
 3. A radioactive material container according to claim 1characterised in that the receptacle is made from metal, glass or aplastics material.
 4. A radioactive material container according toclaim 3 characterised in that the receptacle is made from any one ofhigh density poly(ethylene), poly(propylene), poly(methylpentene),poly(tetrafloroethylene) or aluminium.
 5. A radioactive materialcontainer as claimed in claim 1 characterised in that there is providedat least one further coating of cadmium (13) and one further coating ofcopper (14) both of which cover a substantial proportion of the exteriorsurface of the receptacle or the lead.
 6. A radioactive materialcontainer according to claim 5 characterised in that the cadmium and/orcopper is deposited by an electroplating process.
 7. A radioactivematerial container according to claim 5 characterised in that thecadmium and/or copper have a thickness in the range 0.01-1.0 mm.
 8. Aradioactive material container according to claim 1 characterised inthat the resilient layer is formed from epoxy resin.
 9. A radioactivematerial container according to claim 2 characterised in that thereceptacle is made from metal, glass or a plastics material.
 10. Aradioactive material container as claimed in claim 2 characterised inthat there is provided at least one further coating of cadmium (13) andone further coating of copper (14) both of which cover a substantialproportion of the exterior surface of the receptacle or the lead.
 11. Aradioactive material container as claimed in claim 3 characterised inthat there is provided at least one further coating of cadmium (13) andone further coating of copper (14) both of which cover a substantialproportion of the exterior surface of the receptacle or the lead.
 12. Aradioactive material container as claimed in claim 4 characterised inthat there is provided at least one further coating of cadmium (13) andone further coating of copper (14) both of which cover a substantialproportion of the exterior surface of the receptacle or the lead.
 13. Aradioactive material container according to claim 6 characterised inthat the cadmium and/or copper have a thickness in the range 0.01-1 mm.14. A radioactive material container according to claim 1 in which thefurther resilient layer covers at least a portion of the lead coating.